A savage attack in a Capitol Hill neighborhood over the weekend that left a 29-year-old man in a coma has residents on alert over the increasing frequency of violent crime in an area of the city popular with young professionals.

Since the beginning of the year, the number of robberies in the area has increased by 64 percent over the previous year. While it’s unclear whether Thomas “T.C.” Maslin, who was reportedly struck in the back of the head with a blunt object, was robbed during the Saturday attack, residents in the area say they have noticed an uptick in robberies.

“There’s a sense of more brazenness and more incidents with guns,” said Ivan Frishberg, an Advisory Neighborhood Commission member from the neighborhood where the attack took place. “We had a pretty significant spike in crime last year. The spike was driven by a couple of groups of young people who were specifically targeting people for a smartphone or a purse.”

After that uptick in December and January, police deployed extra resources to the area, and the number of robberies decreased, Metropolitan Police Department Cmdr. Daniel Hickson said. Since July, the frequency of robberies has crept back up, with 14 incidents reported that month. Those incidents were typically snatch-and-grab robberies that were more opportunistic than violent, he said.

“If this is a robbery, it’s obviously a very violent robbery,” Cmdr. Hickson said. “But there is nothing else in this area that is even remotely similar to this.”

According to police reports, investigators are still trying to locate Mr. Maslin’s cellphone to determine if it was possibly stolen when he was attacked. Reports also indicate that his credit card was used Saturday evening, well after he was found unconscious in front of a home in the 700 block of North Carolina Avenue Southeast around 8:30 a.m. Initially the passer-by who discovered him thought he might have suffered a seizure, but doctors found he had severe head trauma.

“We’re used to some underlying level of street crime here, but very, very rarely do we see consequences like this that are so severe,” Mr. Frishberg said.

Mr. Maslin, the husband of Brent Elementary School teacher Abby Maslin, has been unconscious and undergone brain surgery since the attack, the school’s principal Peter Young said in a statement on the school’s website. Friends had last seen him at the Tune Inn Restaurant and Bar, where they had stopped to get some food after attending a Washington Nationals game on Friday night, according to police reports.

Mr. Maslin’s friends left around 12:30 a.m., but he stayed behind to finish his food.

Police are now seeking help in determining Mr. Maslin’s whereabouts from 12:30 a.m. until the time he was found.

Within the boundaries of the police service area that encompasses most of Capitol Hill, 42 robberies committed without the use of a gun and 14 robberies during which a gun was used were reported this year as of Sunday. Last year, there were 28 robberies without guns and eight robberies with guns during the same period. Robberies make up the majority of the neighborhood’s violent crime, with no homicides reported there this year and only seven assaults.

Across the District, reports of robberies and assaults — particularly those involving the use of a handgun — are up this year compared with last year, according to preliminary data from the Metropolitan Police Department. Though homicides are significantly down, overall violent crime is up by 9 percent this year.

In July, well-known D.C. political strategist and Fox News contributor David Mercer also suffered a brain injury during an attack about seven blocks north of the site where Mr. Maslin was found. In that case, which police consider an assault rather than a robbery, the victim suffered a severe cut to the back of his head during an altercation outside a 7-Eleven on Maryland Avenue Northeast after his cellphone was taken by someone inside the store when he put it down to make a purchase.

Cmdr. Hickson said three people of interest have been identified in that case, but that no arrests have been made.